Hypertrophic osteoarthropathy

Imaging description Imaging findings of hypertrophic osteoarthropathy (HOA) may precede the underlying condition by many months. In secondary HOA radiographs reveal symmetrical periostitis consisting of single or multiple layers of new bone formation. Periostitis occurs along the diaphyses and metaphyses of long bones in the lower and upper extremities (Figure 93.1). It is less commonly observed in the metacarpals, metatarsals, and phalanges. Rarely the periostitis can occur in the lower extremities without involvement of the upper extremities. In severe cases, the ribs, clavicles, scapulae, pelvis, and malar bones are involved. Early in HOA the periosteal reaction presents as a single layer but as the condition progresses the periosteal reaction becomes thickened and multilayered, eventually causing increased cortical thickness and an irregular cortical surface. The thickness of the periosteal reaction is time dependent; it becomes thicker and more extensive with longer disease duration (Figure 93.1). Acroosteolysis has been observed in patients with pachydermoperiostosis and with HOA. Bone scintigraphy in HOA is characterized by symmetrical increased uptake along the cortices of the long bones. The radionuclide activity has been shown to be more intense in the lower extremities especially below the knees (Figure 93.1). Involvement of the pelvis and spine is not a feature of HOA and should suggest metastatic disease. The experience in the literature with CT and MRI is limited. CT is reported to show the periosteal reaction surrounding the long bones, and on MRI it is seen as increased signal intensity on T2-weighted images while the elevated periosteum appears as a hypointense rim.